An output voltage (electric strength) of a single electric double layer capacitor cell (hereinafter referred to as a capacitor cell) of an electric double layer capacitor, which is generally used as various power sources, may be as low as a few volts. Therefore, the capacitor cells are manufactured in units of a cell group which contains a plurality of stacked capacitor cells. In each capacitor cell, an electric double layer capacitor is formed in a bag made of aluminum laminate film, having one pair of electrode plates provided at the top thereof.
A plurality of capacitor cells are serially connected to thereby form a cell group, and produce a desired voltage. The electrode plates of the adjacent capacitor cells are connected to each other.
Japanese Patent Laid-open Publication No. 2003-272966 discloses that electrode plates of two adjacent capacitor cells are connected via a rivet and fixed by means of TIG welding. Japanese Patent Laid-open Publication No. 2002-151365 discloses that a plastically deformable connection plate is welded, at both ends thereof, to the electrode plates of two adjacent capacitor cells to thereby attain electrical connection.
As to charging and discharging of the cell group in an electric double layer capacitor, charging and discharging may be performed with respect to the electrodes of the electric double layer capacitor cells at both ends of the serially connected electric double layer capacitor cells, or the cell group. However, the state of charge and discharge may often vary among the respective capacitor cells. Therefore, there is a desire that the charge and discharge states among the respective capacitor cells be uniform. Thus, charge and discharge with respect to each capacitor cell is often controlled based on pre-measured voltages of the electrodes of the serially connected capacitor cells, such that the respective capacitor cells are charged in constant states.
When the voltage of the electrode plate of each capacitor cell is measured to control the charge and discharge amount, as described above, a circuit substrate having a circuit or the like mounted thereon for the control needs to be connected to the cell group.
With such a process, a structure is applicable in which the adjacent electrode plates are formed extending to the above of the circuit substrate and the extending portions are bent and directly fixed to the circuit substrate using screws. Another applicable structure is one in which a cable or the like connected to a respective electrode plate is connected to the circuit substrate.
However, the arrangement in which a long electrode plate of the capacitor cell is formed and directly fixed to a printed board using a screw has a problem that a resistance value of the entire element increases due to the length of the electrode plate, with the result that the resistance value is increased.
A connection method using a cable results in complicated operation, which takes time, and has a problem that the size of the element becomes larger because a space for holding the bundle of cables must be provided.
Still another problem is that the electrode and the cable tend to be easily damaged when the screws are fixed because of the vibration or impact due to the weight of the electrode and/or the screw on the substrate.